Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon, forming integrated circuits.
Lithography is a process in which a layer of photosensitive material is deposited over a material layer, and the layer of photosensitive material is patterned by exposing the layer of photosensitive material to energy through a lithography mask. The layer of photosensitive material is then developed, and the patterned layer of photosensitive material is used as a mask while exposed portions of the material layer are etched away.
There is a trend in the semiconductor industry towards reducing the size of features, e.g., the circuits, elements, conductive lines, and vias of semiconductor devices, in order to increase performance of the semiconductor devices, for example. The minimum feature size of semiconductor devices has steadily decreased over time. As feature sizes diminish, the patterning of conductive lines, transistor gates, and other circuit components becomes more challenging.
In particular, as feature sizes are reduced, the transfer of patterns of lithography masks to semiconductor devices may become inaccurate. Diffraction and other effects in a lithography process or system may cause features formed on semiconductor devices to appear differently than patterns on a lithography mask.
Lithography techniques such as optical proximity correction (OPC) are sometimes used in an attempt to alleviate mask transfer problems. In OPC, serifs are formed on patterns on a mask or the widths or lengths of portions of patterns on a mask are adjusted. However, in some applications, these OPC methods have not been shown to adequately solve mask pattern transfer problems in lithography processes.
Thus, what are needed in the art are lithography masks and methods of manufacture thereof, wherein pattern transfer from a mask to a semiconductor device is improved.